Miguel Panão

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Verified

Miguel verified their affiliation via an institutional email.

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• PhD Mechanical Engineering
• Professor (Assistant) at University of Coimbra

Infodynamics is the study of how information behaves and changes within a system during its development. This study investigates the insights that informational analysis can provide regarding the ramifications predicted by constructal design. First, infodynamic neologisms informature, defined as a measure of the amount of information in indetermina...

Photophoresis, a thermal phenomenon, generates non-contact forces on microparticles in a fluid when exposed to a light beam, such as a laser. These forces depend on the geometrical, thermal, and optical properties of the particles, and aligning these properties in inhomogeneous particles can enhance photophoretic forces. The use of coated-hollow mi...

The transition from fossil fuels to sustainable alternatives is imperative. This research evaluates Hydroprocessed Vegetable Oil (HVO) as a substitute for Jet A-1 in aviation. Focusing on droplet sizes in fuel sprays, which are critical for optimizing combustion, we explore an informational perspective for comparative analysis. Integrating informat...

After reexamining and generalizing the design of tree-shaped flow networks within disc-shaped bodies, the evolutionary direction toward maximum freedom-to-morph of the geometric features with the flow architecture implies paying attention to its thermal and hydraulic performance. In this work, one explores the thickness of a disc as a degree of fre...

In recent years, a significant increase in interest in alternative vehicle power sources has become apparent. Beyond the primary trend, electric drives, there can also be distinguished much less frequently considered pneumatic drives. One could partly attribute the low popularity of pneumatic drives to the relatively low energy density of compresse...

This study revisits the design of tree-shaped flow networks in disc-shaped bodies, focusing on thermal management applications. The key objectives are to achieve equal point distribution along the disk periphery and minimize flow resistance at each bifurcation point. The literature highlights the challenge of balancing fluid and thermal performance...

The Lumped Capacitance Method is an established solution for transient heat conduction when the convective thermal resistance is much larger than the conductive one, but the heat transfer coefficient is considered constant. For this reason, there is no thermal delay after the start of the transient conduction process. This work explores a new appro...

The phenomenon of bubble encapsulation results from droplet impact on a liquid film for specific impact conditions, but there is no established criterion for predicting its onset. Phenomenon visualization from two perspectives, the common lateral perspective and a bottom perspective, provided insights into the dynamics and formation mechanisms. Nam...

The effect of liquid film dynamics in the hydrodynamics of an isolated drop impact is a complex phenomenon and not fully understood. Therefore, in this work, an experimental setup built to characterize the impact of an isolated droplet on heated and unheated liquid films consists of a heating element made of an aluminum block with resistances to pr...

Numerous drop size distributions in sprays fit the Log-Normal. This letter explains the physical origin of this fitting as the exponential growth of drop size diversity. Consequently, the standard deviation of the natural logarithm of drop size acquires physical meaning. The insights retrieved from this explanation include a demonstration that drop...

The application of Constructal theory to the flow design in engineering applications connects the channels’ architecture with their freedom to morph. Assessing the evolution of the flow architecture in Constructal Design requires a core parameter. Svelteness is the best candidate, given its definition as a flow architecture’s intrinsic global geome...

Nozzle configurations that can generate better fuel spray charactersitics for alternative fuels, which may have higher viscosities have been the focus of many research studies in the field of aircraft engines. Flow blurring injector is a two-fluid nozzle that has yielded satisfactory results for altervative fuels. In this paper, modelling of spray...

The fast-spreading of the SARS-CoV-2 virus led to a significant increase in the demand for personal protective equipment (PPE). Healthcare professionals, mainly dentists, work near the patients, increasing their risk of infection. This paper investigates the effectiveness of an air-curtain sealing effect in a newly designed visor developed to reduc...

Photophoresis is a particle-light-induced phenomenon with several applications, such as spectroscopy, 3-Dimensional displays, and nanomanufacturing, to name a few. This work synthesizes, criticizes, and compares the main hydrodynamic and gas-kinetic models developed to quantify photophoretic forces in the slip-flow regime for uniform light beams, c...

Bubble encapsulation is a phenomenon that results from droplet impact on a liquid film for very specific impact conditions. After splashing, the crown liquid sheet starts to bend inwards, and eventually, the jets at the top of the crown merge and form a perfect empty bubble. This bubble bursts due to the impingement of a secondary droplet that fall...

Portable dentistry devices allow medical dentists to perform procedures on patients in their homes. However, considering the recent pandemic context, these procedures raise concerns regarding the potential of infection since high-speed dental handpieces use water sprays to cool the rotating tool. The water spray droplets impacting the mouth of an i...

Bubble encapsulation is a phenomenon that results from droplet impact on a liquid film for particular impact conditions. After splashing, the crown liquid sheet starts to bend inwards, and eventually, the jets at the top of the crown merge and form a perfect empty bubble. This bubble bursts due to the impingement of a secondary droplet that impacts...

In particle engineering, spray drying is an essential technique that depends on producing sprays, ideally made of equal-sized droplets. Ultrasonic sprays appear to be the best option to achieve it, and Faraday waves are the background mechanism of ultrasonic atomization. The characterization of sprays in this atomization strategy is commonly relate...

Dear Colleagues, I am pleased to announce the opening of this Special Issue on applied thermal engineering to celebrate the 10th anniversary of Applied Sciences. This is a recent and long-awaited section of the journal dedicated to the advances of science and technology in thermal engineering. Thermal systems and processes are essential to meet th...

Fiberglass thin blankets with an aluminium coating are often used for fire protection due to their capacity to withstand extreme incident radiant and convective heat fluxes. This article develops a one-dimensional heat transfer model for predicting the temperature distribution for this coated thermal barrier considering the radiant heat flux from t...

Liquid atomization involves several mechanisms transforming a bulk of liquid into small droplets. The atomization efficiency usefulness is questionable considering its low values (0.01-1%). This work presents a general definition for atomization efficiency and explains why the Sauter mean diameter is the appropriate characteristic drop size (and no...

Toda a vida na Terra é possível por causa da energia do Sol. Depois dessa energia ser capturada, pode ser desperdiçada, armazenada, transformada e transmitida. Este livro centra-se no modo como a energia se transmite e quais os mecanismos principais associados a essa transmissão. Por outro lado, como abordagem teórico-prática, o livro procura unir...

The efficiency and ability to control the energy exchanges in thermal energy storage systems using the sensible and latent heat thermodynamic processes depends on the best configuration in the heat exchanger's design. In 1996, Adrian Bejan introduced the Constructal Theory, which design tools have since been explored to predict the evolution of the...

Spray impingement on smooth and heated surfaces is a highly complex thermofluid phenomenon present in several engineering applications. The combination of phase Doppler interferometry, high-speed visualization, and time-resolved infrared thermography allows characterizing the heat transfer and fluid dynamics involved. Particular emphasis is given t...

The production of sprays involves several hydrodynamic and aerodynamic mechanisms to transform a bulk of liquid into small droplets, and the efficiency of this atomization process is an essential parameter in the optimization of atomizer design. This work develops a general definition for the atomization efficiency (ηa) and challenges the notion of...

In aero-engines, the introduction of biofuels is among the best alternatives to fossil fuels, and this change is likely to affect the impact of droplets on interposed surfaces. Under this framework, this work reviews the main morphological hydrodynamic structures occurring upon the impact of a liquid droplet on a wetted surface, using jet fuel and...

Featured Application The work establishes the grounds for the spray characterization using statistical analysis, how to explore it to improve the physical interpretation of spray processes, and advance the methods to report it in a way that further advances spray science. Abstract The statistical characterization of sprays is an essential way of o...

Keynote about three important topics when characterizing sprays from large data produced by a Phase-Doppler Interferometer. 1) Define when an experimentalist should stop measuring using information theory. 2) Characterize sprays through: 2.1) Drop Size Distributions: how we should build drop size distributions with the physical processes in mind;...

Dry-ice particle sprays for thermal management imply the formation of large particles from agglomeration phenomena inside diffusers. This work investigates the effect of the atomizer geometry (relation between height and exit diameter, H/D) on the mechanisms of micro-particles’ agglomeration using divergent diffusers after the expansion nozzle. Hig...

Within the wide possibilities for the resultant outcome of a single droplet impinging upon a liquid film, there is an unstudied phenomenon that seems to be underestimated or forgotten in time. The formation of a bubble by the crown sheet closure at the top after crown splash is the focus of this paper. The phenomenon was deeply studied as well as i...

Over the years, the phenomena obtained when a drop impinges upon a dry, wetted or heated surface have been thoroughly studied. In previous works, the existence of splash was investigated by the authors with the goal of evaluating the possible implementation of biofuels in the civil aviation and it was found an episode of a phenomenon, seldom report...

The present work is aimed at quantifying the effects of ambient pressure in the heat transfer at single injections of a full cone spray over a hot metal surface. The experimental configuration is that of a spray impinging down perpendicularly onto a flat surface located at 55mm inside an injection chamber. The experiments were conducted for prescri...

The growth of the aviation sector triggered the search for alternative fuels and continued improvements in the combustion process. This study addresses the technological challenges associated with spray systems and the concern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This work proposes a ne...

Mold thermal performance has a direct influence on part properties, quality and defects, and mold productivity. Through additive manufacturing, inserts can be developed with features that respect the necessary high complex geometries the part requires and that increase thermal performance. Constructal design is explored as a design tool to produce...

Spray cooling systems usually use liquids to extract large amounts of heat through phase-change vaporization processes. However, in several applications, cooling requirements are transient and an efficient thermal management implies a proper control of the liquid film deposited on the surface. This represents a challenge to the optimization of ther...

The growth of the aviation sector triggered the search for alternative fuels and continued improvements in thecombustion process. This work addresses the technological challenges associated with spray systems and theconcern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This workproposes a new in...

Spray cooling systems are able to remove large amounts of heat due to phase-change. Although vaporization is themost common phase-change process used in applications requiring thermal management, the use of liquids often implies the presence of a liquid film which is known to mitigate cooling performance. Thus, it is worth exploring other approache...

Laser-Doppler measurements of the velocity characteristics of a ground vortex flow resulting from the collision of a wall jet with a boundary layer are analyzed using advanced statistical tools, namely finite mixtures of probability density functions. These are determined by the best fitting to experimental results using a Bayesian approach based o...

Geothermal energy has many attractive qualities stemming from its ability to produce low-carbon base-load power and heat. Emerging technologies such as the EGS concept can greatly increase the worldwide geothermal potential provided that present-day technological limitations are overcome. The best way to decrease the project risk in its early-stage...

Numerical modelling of heat flow and geothermal gradient is a useful tool in the absence of accurate measurements of such parameters when thermal conductivity and radiogenic heat production are known. This work describes a 2D thermal model that simulates the crust thermal state in Central Portugal aiming geothermal applications and more specificall...

The assessment of spray uniformity is an important step in the fabrication of powders in spray drying processes. The most common approach is based on the relative span, but it has its limitations. And, in some cases, it is shown to be less reliable than initially thought. The underlying reason is that it considers certain characteristic parameters...

Laser-Doppler measurements of the velocity characteristics of a ground vortex flow resulting from the collision of a wall jet with a boundary layer are analyzed using advanced statistical tools. Namely, finite mixtures of probability density functions, which determine the best fitting using a Bayesian approach based on a Markov Chain Monte Carlo (M...

The present paper seeks to develop a functional relation to predict the size distribution of secondary droplets arising upon the impact of a gasoline spray onto interposed flat surfaces, which can be extended to a wide range of flow conditions, including those occurring in IC engines. The work follows a semi-empirical formulation based on experimen...

Ultrasonic atomization is a strategy used in industrial spray drying to produce droplets of nearly uniform size, regardless of volumetric flow rate and solvent. In this work, an ultrasonic spray is characterised to assess for spray drying considering different solvents (water, 10% ethanol/water, 20% ethanol/water, acetone). A Phase Doppler interfer...

In this work, the characteristics of droplets produced by a multijet impingement atomization process are measured with a Phase-Doppler Interferometer and statistically described using finite mixtures of weighted probability density functions (pdf). Through this statistical tool, drop size and axial velocity distributions are involved in the physica...

This paper reports an analysis of the physics of atomization processes using advanced statistical tools. Namely, finite mixtures of probability density functions, which best fitting is found using a Bayesian approach based on a Markov chain Monte Carlo (MCMC) algorithm. This approach takes into account eventual multimodality and heterogeneities in...

Thermal management plays a crucial role in the development of efficient electric vehicles. Namely, in the case of energy demands during power peaks, major losses occur in power electronic devices during the vehicle's driving cycle. The flexibility required to efficiently dissipate the energy released in power electronic devices suggests the develop...

The multijet impingement atomization strategy is proposed as a competitive one in designing atomizers with relatively simple geometries, producing sprays from the impact of multiple jets at low-flow rate conditions (< 1.5 l/min). Most theoretical studies have been made for the spray produced by the impact of two jets. However, there are two importa...

The use of multipoint injection systems for HCCI engines requires a mixture composition precisely controlled in order to obtain the optimum auto-ignition timing. The most favorable injection timing to achieve it is when the intake valve is open, in which case the fuel spray interacts with the air flow and impacts onto interposed surfaces where it m...

Laser- and phase-Doppler diagnostic techniques provide information on particle characteristics in the form of discrete probability distribution functions. Most methods assess the amount of information required for an accurate measurement through the first- and second-order moments of these distributions. However, considering that a measurement is t...

In this work, the characteristics of droplets produced by a multijet impingement atomization process are measured with a Phase-Doppler Interferometer and statistically described using finite mixtures of weighted probability density functions (pdf). Through this statistical tool, drop size and axial velocity distributions are involved in the physica...

This paper explores advanced statistical tools, such as finite mixtures of probability distribution functions to better describe drop size distributions obtained experimentally, and improve the physical interpretation of spray impact under cross-flow, in order to assess the fuel/air mixture preparation in IC engines. Considering that fuel sprays ar...

O fenómeno evolução tem sido um dos maiores desafios para o diálogo entre fé e ciência. Se o mundo evoluiu por acaso e necessidade, haverá espaço para a acção de Deus? Se não houver, será então que Deus existe? Será o 'acaso' mais do que mera aleatoriedade? No diálogo entre fé e ciência, o acaso' significa também uma oportunidade para a emergência...

The power dissipation of electronic devices is reaching the limit of the cooling capacity of current heatsinks, demanding new developments in cooling technologies. Moreover, the dissipated power varies with time, reducing the efficiency of the cooling system, unless an Intelligent Thermal Management is applied. In this paper, a control strategy is...

Thermal management plays a crucial role in the development of high-power electronics devices, e.g. in electric vehicles. The greatest energy demands occur during power peaks, implying dynamic thermal losses within the vehicle's driving cycle. Therefore, the need for devising intelligent thermal management systems able to efficiently respond to thes...

This paper analyzes the transient characteristics of intermittent sprays produced by the single-point impact of multiple cylindrical jets. The aim is to perform a transient analysis of the intermittent atomization process to study the effect of varying the number of impinging jets in the hydrodynamic mechanisms of droplet formation. The results evi...

Thermal management is a particularly difficult challenge to the miniaturization of electronic components because it requires high performance cooling systems capable of removing large heat loads at fast rates in order to keep the operating temperature low and controlled. To meet this challenge, the Intermittent Spray Cooling (ISC) concept has been...

Spray-wall impact is an important process in numerous applications such as internal combustion (IC) engines, spray cooling, painting, metallurgy, and many others. This chapter reviews the main challenges in this dynamic thermofluid event and attempts to systematize the knowledge developed in the hydrodynamics of multiple drop impacts and liquid dep...

Spray-wall impact is an important process in numerous applications such as internal combustion (IC) engines, spray cooling, painting, metallurgy, and many others. This chapter reviews the main challenges in this dynamic thermofluid event and attempts to systematize the knowledge developed in the hydrodynamics of multiple drop impacts and liquid depo...

The impingement of fuel spray onto interposed surfaces in an IC engine, equipped either with a direct or an indirect injection system, is a fundamental issue affecting mixture preparation prior to combustion and, therefore, also affecting engine performance and pollutant emissions. In this context, the development of fuel injection systems relies o...

This paper reports an analysis of the physics of atomization processes using a Bayesian approach based on a Markov chain Monte Carlo (MCMC) algorithm, taking into account eventual multimodality and heterogeneities in drop size distributions. This approach allows the identification of subgroups in multimodal or heterogeneous drop size distributions,...

This paper analysis the transient characteristics of intermittent sprays produced by the single-point impact of multiple cylindrical jets. The aim is to better understand the effect of varying the number of impinging jets in the atomization process, considering intermittent sprays which allow a more accurate control of the flow rate. Some considera...

Culture influenced Charles Darwin's vision of the world and indirectly produced dramatic changes in the scientific discipline of Biology. On the other hand, with the development of Biology due to Darwin's contribution, culture changed and its religious dimension is particularly challenged. Here, drawing on the perspective of a culture of communion...

The work presented here investigates a new approach in the development of heat transfer empirical correlations for intermittent spray impingement, based on simultaneous measurements of the spray droplets characteristics and the surface thermal behavior. Conventionally, heat transfer correlations for spray impingement do not consider the temporal va...

In this work, intermittent spray cooling is proposed as a new technological concept to remove heat fluxes with good performance and introduce the potential use of advanced control techniques in the development of thermal management systems. The objective of this research work is to provide further insight into the physics involved in the heat trans...

Cold Combustion” modes are controlled by mixing prior to injection and, therefore, accurate description of the physical phenomena occurring within the intake port (e.g., atomization, spray-wall impingement and mixing) is crucial to further simulate the energy release. Therefore, the accurate modeling of spray/wall interaction processes, including t...

This work addresses the estimation of the measurement uncertainty of discrete probability distributions used in the characterization of sprays. A real-time assessment of this measurement uncertainty is further investigated, particularly concerning the informative quality of the measured distribution and the influence of acquiring additional informa...

The present paper describes an experimental methodology devised to study spray cooling with multiple-intermittent sprays as those found in fuel injection systems of spark-ignition and diesel engines, or in dermatologic surgery applications. The spray characteristics and the surface thermal behaviour are measured by combining a two-component phase-D...

This paper addresses the influence of fuel spray impact on fuel/air mixture for combustion in port-fuel injection engines. The experiments include time resolved measurements of surface temperature synchronized with PDA measurements of droplet dynamics at impact and were conducted to quantify the effects of interactions between successive injections...

The present work is aimed at quantifying the effects of frequency in the heat transfer at multiple-intermittent impacts of a hollow cone spray in a way to contribute to the development of advanced heat transfer techniques. The flow configuration is that of a spray impacting perpendicularly onto an aluminium flat plate located at 55 mm. The experime...

The use of multipoint injection systems for HCCI engines requires a mixture composition precisely controlled in order to obtain the optimum auto-ignition timing. The most favorable injection timing to achieve it is when the intake valve is open, in which case the fuel spray interacts with the air flow and impacts onto interposed surfaces where it m...

A multiple-intermittent spray cooling system is analyzed in terms of the effects of surface temperature and injection frequency on the overall heat flux and cooling performance. The maximum absolute instantaneous heat flux (q″max) removed by the spray after impact occurs earlier than the minimum dimensionless temperature (min(φ)) attained during an...

A fundamental study is reported here on the spray impingement of pulsed sprays on heated surfaces. The experiments consider simultaneous measurements of surface heat flux and droplet characteristics performed with a Phase Doppler Anemometer (velocity, size and flux) prior to impact, to provide a better insight into the interaction between thermal a...

An experimental study is reported in a simplified flow configuration aimed at deriving a correlation for the Nusselt number, which can be used to predict the thermal behavior of intake valves in port-fuel injection systems. The analysis is based on simultaneous measurements of droplets characteristics and surface thermal behavior and is relevant fo...

The present paper addresses an experimental study of the dynamic exchanges between the impact of an intermittent spray and the liquid film formed over the target, based on detailed phase Doppler anemometry (PDA) measurements of droplet size, velocity and volume flux in the vicinity of the impact. The flow configuration is that of a pulsed injector...

This article reports an experimental study on an intermittent gasoline spray impinging onto a flat surface in the presence of a cross flow. The experiments include detailed phase Doppler anemometry (PDA) measurements of droplet size, velocity, and volume flux to quantify the time-dependent fluid dynamic interactions between the spray and the cross...

The present paper reports a complete set of measurements made with a two-component phase Doppler anemometer of the two-phase flow generated at the impact of a transient gasoline spray onto a flat surface. The spray is generated by a pintle injector and the fuel used was gasoline. The measurements of droplet size–velocity were processed to provide t...

Gasoline Direct Injection (GDI) engines are becoming increasingly popular due to the potential to improve power and fuel consumption. The direct injection of gasoline inside an engine is classified in three types: wall-guided; air-guided; and spray-guided (also designated as air-assisted). In the wall-guided, spray impingement on the piston's bowl...

Among the new techniques capable of removing high heat fluxes, spray cooling appears to be a notable method with its ability of removing heat relying on phase-change (nucleate boiling), additionally to the convective heat transfer linked with fluid motion, but optimum performance requires a precise control of the liquid mass rate supplied for cooli...

Instituto Superior Técnico Mechanical Engineering Department Av. Rovisco Pais, 1049 -001 Lisboa; Portugal (1) e-mail: moreira@dem.ist.utl.pt ABSTRACT The present paper reports part of an experimental study conducted to deepen knowledge on the thermal-and fluid dynamic interaction mechanisms of gasoline sprays impacting onto interposed surfaces in s...

The present paper describes an experimental methodology devised to study spray cooling with pulsed sprays combining a two-component Phase Doppler Anemometer with fast response surface thermocouples. The hardware allows simultaneous acquisition of Doppler and thermocouple signals which are processed in Matlab to estimate the time-varying heat flux a...